This invention relates in general to sewing machines and in particular to a new and useful lubricating system and method of establishing a system for lubricating operating parts of a device such as a sewing machine.
In sewing machines in which, for reasons of design, space or economy, the bearing points are embodied not as encapsulated antifriction bearings requiring no maintenance, but as plain bearings, the necessity arises to supply these partly linearly or circularly moving bearings with a lubricant in sufficient amounts. Because the housing is necessarily provided with openings, for example for the take-up lever or a horizontal needle bar, excessive amounts of lubricant in the bearings must be avoided, to prevent lubricant particles from being propelled by the oscillating or rotating parts out of the housing and thus soiling the work.
German Pat. No. 59 3 888 shows a conventional lubricating system using wicks in a number corresponding to the number of bearings or bearing points to be lubricated and having one end in contact with the bearing or the respective guiding surface, and their other end dipped into a common lubricating vessel. To ensure that the moving bearing parts contact the wick ends in the desired manner without tearing the wicks loose, all the wicks must be carefully secured and also exactly adjusted in a tiresome and time consuming way.
It is known from German Pat. No. 634 710 to supply two bearing sleeves of a needle bar link in the head of a sewing machine through a common lubricant carrier. For this purpose, a felt lining connecting to a lubricant supply is secured to a portion of the inside surface of the head. In the zone of the circularly moving bearing sleeve, the head is concentrical with this circular path of motion of the sleeve. The felt lining is secured in this zone and therefore extends concentrically of the path of motion of the bearing sleeve. Thus, during a part of its rotary motion, the bearing sleeve brushes against the felt and takes up some of the lubricant. In the lower dead center position of the needle bar, the linearly moving bearing sleeve contacts the lower portion of the felt lining and is thus lubricated.
In this prior art design, with the machine head conformable to the respective path of motion, only two moving bearing areas are lubricated through a common lubricant carrier. An additional, separate lubricant carrier is needed for a third moving bearing, namely the smaller radius bearing sleeve of the take-up lever.
East German Pat. No. 01 38 686 discloses a lubricating system for sewing machines wherein all the cavities in a bearing area are filled with a lubricant carrier of a soft polyurethane foam. This lubricating system is applicable to hollow shafts having cross bores which lead to bearing points. With bearing points which rotate about an axis in spaced relationship therewith, or which move linearly, a lubricant supply from the interior is very costly. Such a system is therefore unsuitable for lubricating areas located within the head of sewing machine.